High-power permeability core inductance



Jan. 4, 1949. s. J. MAKI HIGH POWER PERMEABILITY CORE INDUCTNCE Filed Nov. 16, 1946 INVENTOR. GEORGE J. MAKI BY j (TTO NEY Patented Jan. 4, 1949 HIGH-POWER. PERMEABILITY CORE INDUCTANCE George J. Maki, Cedar Rapids, Iowa, assigner Collins Radio Company, Cedar Rapids, Iowa, a

corporation of Iowa Application November 16, 1946, Serial No. 710,333

Claims. (Cl. 171-242) This invention relates to electric vinductances and more particularly to inductances employing cores constituted of compacted magnetic powder or so-called high frequency iron.

A principal object of the invention is to provide a. compact and eillcient inductance for use in circuits utilizing heavy power currents at relatively high or radio frequencies.

Another object is to provide a compact and efficient inductance unit of the type employing a core of compressed comminuted magnetic powder, which is capable of` being used in radio frequency circuits operating at high power levels.

A further object is to provide a novel construction for an adjustable inductance of the permeability type which can be efllciently used in circuits operating at high power levels.

A feature of the invention relates to an adjustable inductance employing powdered iron magnetic elements, which are in the form of telescoped open-work or cage-like members providing for free circulation of air throughout the entire unit, thus enabling it to be emciently used in circuits operating at high frequencies and high power levels.

Another feature relates to a more eilicient permeability type inductance having a winding which is effectively enclosed by inner and outer magnetic cores composed of compacted high frequency powdered iron, or similar magnetic material, and having the advantage of acting as a self-shielded unit against external radio frequency fields.

Al further feature relates to a novel construction of permeability inductance which extends the range of usefulness of so-called high frequency powdered iron cores.

A still further feature relates to the novel organization, arrangement and relative location of parts which cooperate to provide an improved inductance unit employing so-called Vhigh frequency powdered iron cores.

In the drawing,

Fig. 1 is an end view of an inductance unit according to the invention.

Fig. 2 is a side view of Fig. 1, with certain portions broken away.

Fig. 3 is a sectional view of Fig. 2, taken along the line 3-3 thereof.

Fig. 4 is a sectional view of Fig. 1, taken along the line 4-4 thereof.

Fig. 5 is a partial view of a modification of Figs. 1-4.

So-called high frequency powdered iron cores employing compacted powder iron or similar magnetic material have come into quite general use in high frequency or radio circuits and the like, because of the peculiar characteristics of such materials in reducing core losses as compared with cores of solid or laminated sheet iron. However, the powdered constituents from which such cores are made, generally require the use of a. special compound or insulation material so as to insure that the finished core will retain its compacted shape with sufncient rigidity and accuracy, and also so as to reduce the interparticle losses at high frequencies. These bonding or insulating agents have comparatively low critical or melting points as compared with the melting point of the associated iron particles. Furthermore, such cores do not have uniform magnetic characteristics at all temperatures. As a result, there is a certain temperature limit beyond which the inductance cannot be operated without destroying, or seriously aiecting, its desirable magnetic permeability and other properties. For this reason, in the past, such powdered iron cores have been confined to use in electric circuits of relatively low power levels, such as in radio receivers and the like.

The present invention, in addition to providing a more eillcient inductance at low power levels, also enables such powdered iron core inductances to be used in radio transmitters, induction heating equipment, and any other apparatus which is required to operate at relatively high power levels.

Referring to the drawing, the device consists of two open-ended cage-like members which are assembled in nested or telescoped relation and with an inductive winding located between the members. One of these cage-like members comprises an annular heading i0, having around its margin a series of circular openings into which are tightly fitted a series of spaced rods i. While the drawing shows twelve such rods, it will be understood that a greater or less number may be employed. The rods may have a drive t in the header openings, and if desired they may be cemented therein so as to form a rigid unit therewith. Fastened coaxially to header i0 by four screws i2, is a tubular coil form i3 of ceramic or other well-known insulating material which possesses low loss characteristics at high or radio frequencies. A fiat ribbon wire inductance il is wound around form i3, and the ends of the winding are provided with lead-in conductors which are brought out, for example, through suitable openings i5 in the header ill.

Likewise, the other cage-like member comprises an annular header i6 which has a series of openings into which are tightly fitted a corresponding series of rods il, preferably equal in number to the rods Il and in radial alignment therewith as shown more clearly in Fig. 14. In that case, the rods i1 will be of smaller cross-sectional diameter than the rods Il. Rods i1 are located closer to the axis of header i6, than are the rods il with respect to the axis of header Hi, thus providing an annular space within which the form Il and its winding il are located. It will be observed that the rods ii and I1 are of the same length, so that when the two cage-like members are fully telescoped as shown in Figs. 2 and 3, the free ends of rods II abut against header I6, and the free ends of rods I1 abut against the headerV I0, thus providing a complete magnetic circuit which envelopes winding I4. In accordance with the invention, headers Ill and I6 and their respective rods Il and I1, are formed of compacted comminuted magnetic ma#- terial, such as powdered high frequency iron of the kind well-known in so-called permeability tuners. Examples of such materials are described in U. S. Patents #1,274,952 and $121,609,745. If desired, the headers and their respective rods may be integrally molded or compacted as a unit from a suitable batch of the powdered magnetic material which contains a suitable bonding agent as is well-known in the art.

When the unit is to be used as a xed inductance, the two nested cage-like members may be held in abutting relation .by a'suitable clamp or fastening screws I8 (Fig. 5). However, when the unit is to be used as an adjustable inductance, the header I with its rods I I may be suitably fastened to a rigid support, and the header I6 with its rod I1 may be slidably supported on suitable guides (not shown), so that it may be adjustably telescoped into and out of the coil form I3 to vary the inductance of the winding I4 in the well-known way, as indicated by the arrows adjacent the header I6 in Fig. 2.

From the foregoing description, it will be seen that the inductance unit is capable of dissipating a large amount of heat energy by reason of the fact that there is a clear path through the annular openings I9 and 20 and through the form I3. Likewise, because of the open-work structure provided by rods II and I1, there is free air circulation both interiorly and exteriorly of the coil and its form. This enables the device to be used in electric circuits' of high power levels without danger of the magnetic core material exceeding a temperature at which its desired magnetic permeability and other characteristics are deleteriously affected. By providing the inductance coil with the powdered iron rods exterlorly and interiorly and by completing the magnetic circuit through respective headers I0 and I6, an efficient closed magnetic circuit for the inductance Winding is provided. This greatly increases the inductance of the winding and renders it possible to use a shorter length of wire with fewer" turns to achieve a given inductance. This also improves the "Q of the coil and results in a higher eiciency for the tuned circuit with which the idnuctance is to beused.

While4 one particular embodiment has been described herein, it will be understood that various changes and modifications may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. An inductance unit comprising an inductance winding, and a magnetic core therefor, said core comprising a pair of concentric circumferentially spaced members each constituted of compacted high frequency magnetic powder, and each comprised ofva header having a plurality of spaced risers therefrom.

2. An inductance unit comprising an inductance winding, a pair of telescoped members between which said winding is located, each of said members being constituted of compacted comminuted magnetic material, and each comprised 4 of a header having a plurality of spaced risers therefrom.

3. An inductance unit comprising an inductance winding, an inner open-work core member, a surrounding outer open-work core member, said winding being located between said members, and means completing the magne"c circuit between both of said members, said members each being constituted of compacted powdered high frequency iron.

4. An inductance unit comprising yan inductance winding, an inner open-work core member,

an outer open-work core member, said members surrounding each other and having said Winding located therebetween, and header members at each end of said open-work members for completing the magnetic circuit therebetween, said open-work members and said headers each being constituted of comminuted high frequency iron.

5. An inductance unit for use at high frequencies comprising a pair of nested core members each comprising a header carrying a series of spaced rods, the headers and rods being constituted of compacted powdered magnetic material, and an inductance winding located between the said nested members.

6. An inductance unit according to claim 5 in which said members are adjustably telescoped to control the eiective inductance of the unit.

7. An inductance unit for use at high frequencies comprising means to support an inductance winding, a first set of spaced rods extending interiorly through said support means, a second set of spaced rods extending parallel to the first rods but exteriorly of said support means, and means completing a magnetic circuit between both said sets of rods, the lastmentioned means and said rods being constituted of compacted comminuted high frequency iron.

8. An inductance of the permeability core type comprising a first annular header carrying a rst set of spaced rods, a second annular header carrying a second set of spaced rods in peripheral spaced relation to the rst set of rods, and an inductance winding located between the said first and second sets of rods, said rods and said headers being constituted of compacted comminuted magnetic material.

9. A high frequency inductance of the permeability core type, comprising a pair of headers, means completing a magnetic circuit between said headers, said means being in the form of two telescoped sets of open-work magnetic members between which an inductance winding is located, said headers and open-work members being constituted mainly of comminuted magnetic material.

10. A high frequency inductance of the permeability core type, comprising an annular header carrying a series of spaced rods extending therefrom, to form an open-ended cage-like member, said header and rods being constituted of compacted and comminuted high frequency iron, and a magnetizing winding telescoped with respect to said rods.

GEORGE J. MAKI.

REFERENCES CITED FOREIGN PATENTS Country Date France i--- Feb. 27, 1933 Number 

